1. Field of the Invention
This invention relates to a speaker apparatus for transducing electrical signals into acoustic sound in which the apparatus can be reduced in thickness.
2. Description of the Related Art
There has hitherto been used a speaker apparatus in which the sound in the high frequency range and the sound in the mid to low frequency range are reproduced with respective different vibrating plates. As this speaker apparatus, there is proposed a coaxial two-way speaker apparatus in which a vibrating plate reproducing the sound of a high frequency range and another vibrating plate reproducing the sound of the mid to low frequency range are arranged superimposed with the centers in the vibrating direction coincident with each other.
As this type of speaker apparatus, one arranged as shown in FIG. 1 is proposed. A speaker apparatus 101, shown in FIG. 1, includes a vibrating system for the high sound range 105 for generating the acoustic sound of a high sound range, a magnetic circuit for high sound range 106 for driving the vibrating system for the high sound range 105, a vibrating system for the mid to low sound range 107 for generating the acoustic sound of a mid to low sound range, and a magnetic circuit for mid to low sound range 108 for driving the vibrating system for the vibrating system for the mid to low sound range 107.
The vibrating system for the high sound range 105 is supported by a frame 109 and includes a dome-shaped vibrating plate 110, a cylindrically-shaped bobbin 111, carrying one end of the vibrating plate 110, and a resilient edge 112 connected to the outer rim of the vibrating plate 110.
The magnetic circuit for high sound range 106 includes a voice coil 114, for vibrating the vibrating system for the high sound range 105, a yoke 115 for forming a magnetic path, a magnet 106 for according the magnetic flux to the yoke 115, and a top plate 117 provided adjacent to the magnet 116 for defining a magnetic gap. The voice coil 114 is provided on the outer periphery of the bobbin 111 of the vibrating system for the high sound range 105 within the magnetic gap. Both ends of the voice coil 114 are connected via a braided wire, not shown, to a connection terminal 110 provided on the outer rim of the frame 109. The yoke 115 is formed of a magnetic material in a disc shape and has an upstanding columnar center pole 118. This center pole 118 is inserted into the inside of the bobbin 111 of the vibrating system for the high sound range 105. The magnet 116, mounted on the yoke 115, has a ring shape into which is inserted the center pole 118. This magnet 116 has the yoke side and the top plate side magnetized to an S-pole and to an N-pole, respectively. The yoke 115 has its position adjacent to the S-pole side of the magnet 116 magnetized to an S-pole. The magnet 116, mounted on the yoke 115, has a ring shape, with a center opening into which is inserted the center pole 118. The top plate 117, magnetized to an N-pole, has a magnetic gap defined between its inner rim and the outer rim of the center pole 118.
The magnetic circuit 106 is covered by a shield cover 119 for prohibiting the magnetic flux from leaking from the magnetic circuit 106 to outside, as shown in FIG. 1.
Referring to FIG. 1, the vibrating system for the mid to low sound range 107 includes a substantially conically-shaped vibrating plate 120, having a center through-hole, a cylindrically-shaped bobbin 121, having its one end mounted in a through-hole in the vibrating plate 120, a resilient edge 122, connected to the outer rim of the vibrating plate 120, and a resilient vibration-absorbing damper 123 mounted on the bobbin 121.
Referring to FIG. 1, the magnetic circuit for mid to low sound range 108 includes a voice coil 124 for vibrating the vibrating system for the mid to low sound range 107, a yoke 125 forming a magnetic path, a driving magnet 126 for according the magnetic flux to this yoke 125, a top plate 127 provided adjacent to the driving magnet 126 for defining the magnetic gap and a cancelling magnet 128 for prohibiting the magnetic flux of the driving magnet 126 from leaking to outside of the magnetic circuit for mid to low sound range 108.
The voice coil 124 is provided on the outer rim of the bobbin 121 of the vibrating system for the mid to low sound range 107 within the magnetic gap. Both ends of the voice coil 124 are connected to the connection terminal 110 provided on the outer rim of the frame 109 via a braided wire 130. The yoke 125 is formed of a magnetic material in a disc shape and has an upstanding columnar center pole 131. This center pole 131 is inserted into the inside of the bobbin 121 of the vibrating system for the mid to low sound range 107. The driving magnet 126, provided on the yoke 125, has a ring shape with a center opening into which is inserted the center pole 131. This driving magnet 126 has the yoke side and the top plate side magnetized to an S-pole and to an N-pole, respectively. The yoke 125 has its position adjacent to the S-pole side of the driving magnet 126 magnetized to an S-pole. The top plate 127, mounted on the driving magnet 126, has a ring shape into which is inserted the center pole 131. The top plate 127, magnetized to an N-pole, has a magnetic gap defined between its inner rim and the outer rim of the center pole 118. The cancelling magnet 128 has a ring shape and is provided on the rear end of the yoke 125. The cancelling magnet 128 has the yoke side and the rear end magnetized to the S-pole and to the N-pole, respectively.
This speaker apparatus 101 has a frame 109 supporting the vibrating system for the mid to low sound range 107, as shown in FIG. 1. This frame 109 is formed of a metallic material and substantially conically shaped and flared from the rear end towards the front end. The frame 109 has, on its front end side, a holder 132 for holding the vibrating system for the mid to low sound range 107. To this holder 132 is secured the outer rim of the edge 122 of the vibrating system for the mid to low sound range 107 via a gasket, not shown.
In the above-described speaker apparatus 101, if the current is fed to the voice coils 114, 124, the voice coils 114, 124 are set into vibrations and, in keeping with the vibrations of the voice coils 114, 124, the vibrating plates 110, 120 of the vibrating system for the high sound range 105 and the vibrating system for the mid to low sound range 107 are set into vibrations to produce the acoustic sound.
Referring to FIG. 2, a modified speaker apparatus 102, having a vibrating system for the high sound range 135 and a magnetic circuit for high sound range 136 different from those of the above-described speaker apparatus 101, is explained. Since the vibrating system for the mid to low sound range and the magnetic circuit for mid to low sound range of the speaker apparatus 102 are similar to the vibrating system for the mid to low sound range 107 and to the magnetic circuit for mid to low sound range 108 of the above-described speaker apparatus 101, shown in FIG. 2, corresponding parts are depicted by the same reference numerals and are not explained specifically.
Referring to FIG. 2, the vibrating system for the high sound range 135 is supported by the magnetic circuit for mid to low sound range 108, and includes a dome-shaped vibrating plate 140, a cylindrically-shaped bobbin 141, carrying one end of the vibrating plate 140, and a resilient edge 142 connected to the outer rim of the vibrating plate 140.
The magnetic circuit for high sound range 136 includes a voice coil 144, for vibrating the vibrating system for the high sound range 135, a bottomed tubular yoke 145 for forming a magnetic path, a magnet 146 for according the magnetic flux to the yoke 145, and a top plate 147 provided adjacent to the magnet 146 for defining a magnetic gap. The voice coil 144 is provided on the outer periphery of the bobbin 141 of the vibrating system for the high sound range 135 within the magnetic gap. Both ends of the voice coil 144 are connected via a braided wire, not shown, to a connection terminal 110 provided on the outer rim of the frame 109. The yoke 145 is formed of a magnetic material. This magnet 146 has the yoke side and the top plate side magnetized to an S-pole and to an N-pole, respectively. The yoke 145 has its position adjacent to the S-pole side of the magnet 146 magnetized to an S-pole. The top plate 147, mounted on the magnet 146, is formed of a magnetic material in a disc shape. This top plate 147, delimiting a magnetic gap between its outer rim and the inner rim of the opening end of the yoke 145, is magnetized to an N-pole.
In the above-described speaker apparatus 102, if the current is fed to the voice coils 124, 144, the voice coils 124, 144 are set into vibrations and, in keeping with the vibrations of the voice coils 124, 144, the vibrating plates 140, 120 of the vibrating system for the high sound range 135 and the vibrating system for the mid to low sound range 107 are set into vibrations to produce the acoustic sound.
The above-described conventional speaker apparatus 101 has a drawback that the sound source for the high frequency range obstructs the reproduced sound of the sound source for the mid to low frequency range to affect reproduced sound pressure versus frequency characteristics.
Thus, it is in general critical to approach and match the mounting positions of the sound source for the high frequency range and the sound source for the mid to low frequency range to each other. However, this speaker apparatus 101 has a drawback that the positions of the voice coils 114, 124 constituting the respective sound sources are spaced apart in the fore-and-aft direction in the amplitude direction, as shown in FIG. 1.
In the above-described speaker apparatus 102, since the sound source for the high frequency range is separated from the amplitude plane of the vibrating plate 120 of the sound source for the mid to low frequency range, as shown in FIG. 2, the sound source for the high frequency range is prevented from affecting the reproduced sound pressure versus frequency characteristics. However, this speaker apparatus 102 is not desirable in that the sound sources are not positioned in the same plane relative to the playback sound pressure direction.
The above-described speaker apparatus 101, 102 suffer from the problem that the magnet of a larger magnetic power is used to reduce the size of the sound source for higher frequency range, thus raising the production cost. These speaker apparatus 101, 102 are inconvenient in that a magnetic circuit for the sound source for higher frequency range has to be provided separately to increase the number of component parts to detract from ease in assembling.